Why do Oliver and the Duchess need each other in "The Duchess and the Jeweller"?
The Duchess of Lambourne needs Oliver to provide her with the money to pay her gambling debt, and Oliver needs her to provide him the opportunity to court her daughter Diana because he is not royalty.
As the story opens, Oliver Bacon seems to have all that he desires as he opens invitations from prestigious people: "duchesses, countesses, viscountesses, and Honorable Ladies." He is the richest jeweler in all of England. He stands before a portrait of his mother, telling her "I have won my bet." However, he is yet
...a dissatisfied man, a man who seeks something that is hidden, though he had won his bet.
When the Duchess of Lambourne appears at his shop, Bacon purposely makes her wait ten minutes. Nevertheless, the Duchess understands that she has power over the commodity that he desires. She pulls from her bag a leather pouch that contains pearls, pearls she says are from the Appleby cincture, an ornamental belt. Oliver is tempted to have them tested; then he stops. "Arminta, Daphne, Diana," she moaned. "It's for them."
"Diana"--the name of the beauty he desires, the "commodity." Oliver imagines himself in a white waistcoat with the Prime Minister, at a dinner of trout and other delicacies. Then, he pictures a ride in the woods alone with Diana. So, he decides not to verify the pearl's quality; instead, he writes a check in the amount of twenty thousand pounds for the pearls.
They were friends, yet enemies; he was master, she was mistress; each cheated the other, each needed the other, each feared the other...
Oliver feels no real sense of achievement because he and the Duchess have measured everything as a commodity.